I need two different layouts for bundles. For this I created an alternative page layout in the page_layout folder. I am able to access the page layout in the backend of the bundle what works like a charm.

Now I need to have an alternative XML-definition for the bundle-layout.

The original file is called: catalog_product_view_type_bundle.xml

I would like to use an alternative, like:catalog_product_view_type_bundle_alternative.xml

.xml files are created according to handler. In your case did you created it? In your case best way to add class to body is from code i.e. if some logic then add class to body. Let me know if you need to add class through code.
– Sukumar GoraiAug 21 '18 at 9:17

Or you would need to add a new product type BundleAlternative to have catalog_product_view_type_bundle_alternative.xml working. But I find the question not clear enough. a) Do you want to use a different layout for bundle? b) Do you want to use 2 different layouts for bundle (like an a/b test)? c) Or do you want another bundle product that has a different layout? d) ?
– sterosAug 21 '18 at 9:33

To add a class is just one thing I want to achieve. There are also other CSS- and JS-resources I would like to add. I know how to do it in the original file. The question is how to connect the alternative layout in the backend with this alternative file: catalog_product_view_type_bundle.xml.
– user3631648Aug 21 '18 at 9:33

Sorry for not being that clear: I would like to have 2 different layouts for bundle (like a/b test). These both layouts should have different classes, CSS- and JS-resources. (I am going to clarify this in the question, thanks you steros).
– user3631648Aug 21 '18 at 9:38